QD 


Anomalous  Osmosis  with  Gold  Beaters  Skin 

Membranes,  and  the  Relation  of  Osmosis 

to  Cell  Potential 


A  DISSERTATION 

SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS  FOR 

THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY  IN 

THE  UNIVERSITY  OF  MICHIGAN 


BY 

ORIN  EDWARD  MADISON 
1918 


EASTON,  PA.: 

ESCHSNBACH  PRINTING  Co. 
1921 


Anomalous  Osmosis  with  Gold  Beaters  Skin 

Membranes,  and  the  Relation  of  Osmosis 

to  Cell  Potential 


A  DISSERTATION 


SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS  FOR 

THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY  IN 

THE  UNIVERSITY  OF  MICHIGAN 


BY 

ORIN  EDWARD  MADISON 
1918 


EASTON,  PA.; 

ESCHBNBACH  PRINTING  Co. 
1921 


The  author  wishes  gratefully  to  express  his  indebted- 
ness and  gratitude  to  Professor  Floyd  E.  Bart  ell,  under  whose 
direction  this  research  was  carried  out,  in  most  sincere  apprecia- 
tion of  invaluable  advice,  kindly  encouragement,  helpful 
criticism,  and  many  personal  favors  throughout  the  course 
of  the  work. 


CONTENTS 
I.  HISTORY 

Discovery  of  the  Phenomenon  of  Osmosis 5 

First  Quantitative  Experiments  on  Osmosis 5 

Later  Work  of  Graham  and  Others,  and  their  Views  as  to  the  Cause  of 

Osmosis 6 

Similarity  Between  Anomalous  Osmose  and  Electric  Osmose 7 

Electric  Osmose  and  Adsorption 8 

II.  THEORETICAL  CONSIDERATIONS 

Introduction 9 

Capillary  System  and  Membrane  System 9 

Adsorption  Potentials 9 

Possible  Electrical  States  Associated  with  the  Membrane  and  Capillary 

Systems 10 

Examples  of  Each 12 

III.  EXPERIMENTAL  PART 

Apparatus  and  Methods 13 

a.  Two-Compartment  Cell 15 

b.  One-Compartment  Cell 16 

Osmose  of  Chlorides  in  One-Compartment  Cell 16 

Osmose  of  Chlorides  in  Two-Compartment  Cell 18 

Osmose  of  Nitric  Acid 20 

Osmose  of  Sodium  Hydroxide 20 

Measurement  of  Cell  Potential 21 

The  Electromotive  Force  of  0 . 05  M  Chlorides  against  Water 22 

The  Electromotive  Force  of  Nitric  Acid  and  of  Sodium  Hydroxide  against 

Water 23 

Summary  and  Conclusions 23 

Osmose  of  0 . 05  M  Chlorides  in  Two-Compartment  Cell 23 

a.  Acid  throughout  the  Cell 28 

b.  Acid  on  the  Solution  Side 29 

c.  Acid  on  One  Side;  Solution  on  the  Other  Side 32 

d.  Alkali  throughout  the  Cell 33 

The  Electromotive  Force  of  0 . 05  M  Chlorides  with  Nitric  Acid  throughout 

the  Cell 35 

The  Electromotive  Force  of  0 . 05  M  Chlorides  with  Sodium  Hydroxide 

throughout  the  Cell 35 

Summary ., 35 


458723 


ANOMALOUS    OSMOSIS  WITH  GOLD  BEATERS  SKIN 

MEMBRANES,  AND  THE  RELATION  OF  OSMOSIS 

TO  CELL  POTENTIAL 

The  phenomenon  of  osmosis  appears  to  have  been  dis- 
covered in  1748  by  Abbe  Nolle!.1  He  filled  a  vessel  with  alco- 
hol, closed  it  with  bladder,  and  submerged  the  whole  in  pure 
water.  The  volume  of  the  alcohol  was  increased  and  the 
bladder  distended,  thus  showing  that  the  water  had  passed 
through  the  membrane  more  rapidly  than  the  alcohol. 

This  discovery,  however,  was  accorded  little  attention  in 
scientific  circles  outside  that  of  medicine  and  was  apparently 
forgotten  until  1819  when  Sommering2  made  a  similar  discovery. 
He  found  that  when  a  hog's  bladder,  filled  with  an  alcohol- 
water  solution,  was  suspended  in  air,  the  alcohol  became  more 
concentrated.  When  the  experiment  was  repeated  using  an 
India  rubber  bag,  the  alcohol  became  more  dilute.  These  two 
opposite  effects  with  different  membrane  materials  early  estab- 
lished the  importance  of  the  nature  of  the  membrane  itself. 

The  first  quantitative  experiments  on  osmosis  were  car- 
ried out  by  Dutrochet3  and  Vierordt4  between  the  years  1826 
and  1848.  They  found  that  when  a  salt  solution  was  separated 
from  water  by  means  of  pig's  bladder,  the  water  diffused 
through  the  membrane  more  readily  than  the  salt  solution, 
thus  producing  a  hydrostatic  pressure.  Dutrochet  observed 
that  there  was  always  a  current  inward  to  the  more  concen- 
trated solution  side;  this  he  called  the  endosmotic  current. 
Simultaneously  there  was  an  outward  current  which  he  called 
the  exosmotic  current.  In  1827  Dutrochet5  brought  forth 
an  electrical  theory  to  explain  osmosis.  He  concluded  that 
the  two  sides  of  the  membrane  developed  different  "degrees 
of  electricity,"  but  that  the  difference  could  not  be  detected 
with  a  galvanometer.  The  researches  of  Dutrochet  and 
Vierordt  established  the  fact  that  the  difference  between 
the  rates  of  diffusion  of  pure  water  and  of  salt  solutions  de- 
pended not  only  on  the  concentration  of  the  solution,  but  also 
on  the  nature  of  the  salt  solution  and,  as  they  later  found,  on 
the  nature  of  the  permeable  septum  used.  Dutrochet  also 
found  that  osmotic  pressures  were  developed  by  porous  in- 
organic membranes  as  well  as  by  organic  membranes. 


About  twenty-five  years  later,  extensive  investigations 
were  carried  out  by  Thomas  Graham,6  who  used  a  variety  of 
membranes,  both  organic  and  inorganic,  with  many  different 
types  of  solutions.  He  obtained  osmotic  effects  covering  a 
wide  range  of  magnitude.  Certain  anomalous  effects  he 
attributed  mainly  to  the  chemical  disintegration  of  the  mem- 
branes; in  fact,  he  advanced  the  theory  that  an  alteration  of 
the  membrane  was  an  indispensable  condition  to  the  mainte- 
nance of  the  " osmotic  force."  He  considered  that  one  side 
of  the  membrane  was  always  acid  and  the  other  side  alkaline. 
The  direction  of  the  endosmotic  current,  he  believed,  was  al- 
ways from  the  acidic  to  the  basic  side.  The  effects  he  ob- 
tained with  organic  membranes  were  generally  opposite  to 
those  he  obtained  with  unglazed  porcelain;  however,  he 
offered  no  explanation  for  this  difference  in  behavior.  Later, 
influenced  by  his  own  work  on  dialysis,  and  by  the  work  of 
L/Hermite7  on  selective  or  preferential  solubility  of  two  liquids 
in  a  separating  membrane,  Graham  came  to  the  conclusion 
held  by  Liebig8  that  osmosis  is  due  to  the  ability  of  the  mem- 
brane to  absorb  the  separated  liquids.  From  this  time  on  for 
nearly  half  a  century  the  work  on  osmosis  was  directed  mainly  to 
the  study  of  unidirectional  currents.  "Semi-permeable"  mem- 
branes were  used  which  were  capable  of  producing  maximum 
osmotic  pressures.  It  had  been  pointed  out  by  van't  Hoff9  that 
such  pressures  were  expressible  by  the  gas  law  formulations. 

As  work  progressed  and  quantitative  data  increased, 
many  of  the  investigators  in  this  field  appear  to  have  almost 
entirely  neglected  to  take  into  account  the  fact  that  anomal- 
ous osmotic  effects  of  considerable  magnitude  are  obtained  when 
solutions  of  electrolytes  are  used  with  osmotic  membranes. 
Abnormal  effects  were  in  nearly  all  cases  attributed  either  to 
electrolytic  dissociation,  or  to  molecular  association,  or  to 
hydration.  The  attention  of  these  investigators  has  for  the 
most  part  been  directed  to  a  study  of  the  more  perfect  semi- 
permeable  membranes  such  as  copper  ferrocyanide  with  solu- 
tions of  non-electrolytes  such  as  sugar. 

The  tendency  of  electrolytes  to  produce  osmotic  pressures 


at  variance  with  the  values  calculated  from  van't  Hoff's 
generalization,  even  with  the  best  of  "semi-permeable"  mem- 
branes, is  easily  detected  when  sufficiently  refined  measure- 
ments are  made.  This  has  been  clearly  shown  by  Lord 
Berkeley  and  E.  G.  J.  Hartley10  Morse  and  his  collaborators,11 
and  by  other  investigators  who  have  observed  the  lack  of 
conformity  between  the  experimental  and  the  calculated  values 
of  osmotic  pressures  of  salt  solutions.  No  generally  accepted 
theory  has  been  given  to  account  for  this  osmotic  behavior. 

The  anomalous  effects  of  salt  solutions  with  natural  cells 
and  tissues  in  the  presence  of  an  acid  or  alkali  medium  has  been 
a  perplexing  problem  and  has  been  studied  by  Girard,12 
Lillie,13  Osterhout,14  Loeb15  and  others. 

Girard  studied  the  osmotic  pressures  of  electrolytes 
with  various  animal  membranes.  He  found  that  the  os- 
motic pressures  of  electrolytes  vary  greatly  with  their  nature, 
as  well  as  with  their  concentration;  in  fact,  he  noted  that  in 
some  cases  the  exosmotic  current  was  greater  than  the  endos- 
motic  current,  i.  e.,  negative  osmosis  was  obtained.  In 
seeking  an  explanation,  Girard  announced  his  electrostatic 
theory.  He  considered  osmosis  of  electrolytes  to  be  due 
primarily  to  an  electrical  effect,  and  the  process  of  osmosis 
to  be  dependent  mainly  upon  two  electrical  factors:  (i)  the 
sign  of  the  charged,  movable,  liquid  layer  adjacent  to  the 
walls  of  the  capillaries  in  the  membrane,  and  (2)  the  difference 
of  potential  existing  between  the  two  faces  of  the  membrane. 
He  regarded  the  membrane  as  being  electrically  charged.  He 
considered  the  charge  on  the  walls  of  the  capillaries  to  be  due 
to  the  effect  of  a  small  excess  of  hydrogen  or  hydroxide  ions. 
The  movable  layer  of  liquid  within  the  capillary  was  assumed 
to  possess  a  charge  opposite  to  that  of  the  capillary  wall. 
Girard  found  that  the  difference  of  potential  between  two  solu- 
tions with  a  membrane  interposed,  may  be  greater  or  less  than 
the  potential  between  the  two  solutions  when  in  direct  con- 
tact, and  further,  that  the  orientation  of  the  cell  system 
may  even  be  reversed  by  the  interposition  of  the  membrane. 
A  reversal  of  this  kind  means  that  the  sign  of  the  interface 
potential  has  been  changed. 


It  appears  to  be  the  rule  that  permeable  membranes  of 
almost  any  material  whatever,  interposed  between  a  solution 
and  water,  or  between  two  solutions,  give  differences  of  poten- 
tial between  the  two  faces  of  the  membrane  which  are  differ- 
ent from  the  contact  potential  of  the  two  liquids.  Examples 
of  such  potential  differences  exhibited  by  membranes  are  to 
be  found  in  the  work  of  Brtinings,16  Lillie,17  Loeb,18  Beutner,19 
Bartell  and  Hocker,20  and  others. 

The  precise  nature  of  the  membrane  seems  to  be  an  im- 
portant factor  in  determining  the  nature  of  the  osmotic  effect 
and  the  electrical  condition  of  a  cell  system.  The  propor- 
tionality which  has  been  shown  to  exist  in  osmotic  cell  systems 
between  the  osmosis  measured  in  terms  of  hydrostatic  pressure 
and  the  E.  M.  F.  of  the  same  cell  system  seems  to  conform 
fairly  closely  to  Wiedemann's  third  law21  for  electrical  osmose, 
which  states  that  for  a  given  diaphragm  material,  the  differ- 
ence in  hydrostatic  pressure  maintained  between  the  two 
sides  of  the  porous  diaphragm  is  proportional  to  the  applied 
potential.  Further  analogies  may  be  shown  to  exist  between 
the  phenomena  of  anomalous  osmose  and  that  of  electrical 
osmose;22  for  example,  in  both  cases  a  reversal  of  flow  of 
liquid  can  be  brought  about  by  the  introduction  of  acid,  base, 
or  a  salt  of  polyvalent  ions,  into  the  cell  system.  Both  phe- 
nomena are  dependent  upon  the  existence  of  an  electrical 
double  layer  along  the  walls  of  the  capillary  pores. 

In  the  process  of  electrical  osmose,  a  difference  of  poten- 
tial is  enforced  upon  the  cell  system  and  is  caused  to  be  opera- 
tive within  the  two  solutions  which  bathe  the  two  faces  of 
the  membrane;  whereas  in  the  process  of  anomalous  osmose 
the  difference  of  potential  is  self-induced,  and  it  too  may  be 
assumed  to  function  between  the  two  faces  of  the  membrane. 
The  effects,  resulting  in  a  flow  of  solution  through  the  mem- 
brane, are  the  same  in  either  case. 

Freundlich,23  influenced  by  his  own  work  on  adsorption 
and  by  the  theories  of  Perrin24  regarding  the  analogies  be- 
tween the  behavior  of  suspensions  and  the  peculiarities  of 
electrical  osmose,  was  probably  the  first  to  point  out  clearly 


the  intimate  relations  existing  between  adsorption  and  elec- 
trical osmose.  Bancroft25  has  further  contributed  to  our 
understanding  of  the  relation  between  the  sign  of  the  charge 
on  a  membrane  and  the  selective  adsorption  of  anion  or  cation. 
It  is  only  a  short  step  forward  to  apply  to  osmotic  phe- 
nomena, which,  as  above  stated,  have  been  shown  to  be  very 
similar  fundamentally  to  electrical  osmose,  a  definite  theory 
based  upon  selective  or  preferential  adsorption  of  ions. 

Theoretical 

In  attempting  to  explain  the  osmose  of  electrolytes  by 
an  electrical  theory  similar  to  that  used  to  account  for  elec- 
tric osmose,  two  determining  factors  must  always  be  con- 
sidered: (i)  the  electric  charge  of  the  capillary  pore  wall  in 
respect  to  the  charge  on  the  liquid  layer  bathing  this  wall 
(i.  e.,  the  Helmholtz  electrical  double  layer),  represented  in 
Fig.  I,  which  we  shall  refer  to  as  the  capil- 
system>'  an(^  (2)>  ^e  orientation  of  the 
electrical  potential  existing,  between  the  two 
faces  of  the  membrane,  represented  in  Fig.  II, 
which  we  shall  refer  to  as  the  membrane  system. 

The  magnitude  of  these  two  electrical  factors  is  dependent 
upon  the  extent  of  diffusion  of  electrolyte  through  the  mem- 
brane, upon  the  relative  migration  velocities  of  the  ions  and 
upon  the  extent  of  selective  ion  adsorption.  These  three  fac- 
tors are  operative  simultaneously  and,  since  each  factor 
affects  to  some  degree  the  effect  of  the  others,  the  result  ob- 
tained is  necessarily  a  differential  one,  it  being  the  combined 
effect  of  all  three  factors ;  any  one  factor  may  play  a  predominat- 
ing part  in  any  particular  case.  The  value  of  the  electrical 
charges  may  be  materially  altered  by  even  traces  of  acids  or 
alkalis. 

It  has  been  pointed  out  by  Bancroft26  that  adsorption  is 
a  specific  process,  the  neutralization  of  the  charge  on  a  given 
colloid  depending  on  the  nature  of  the  colloid,  and  upon  the 
nature  of  both  cation  and  anion.  This  harmonizes  with  the 
view  of  Freundlich,27  Michaelis28  and  others  that  adsorption 


IO 


potentials  are  dependent  upon  the  nature  of  the  adsorbing 
material  and  upon  the  extent  of  selective  ion  adsorption.  It 
seems  probable,  then,  that  the  sign  of  the  charge  upon  the 
capillary  pore  wall  of  an  osmotic  membrane  is  dependent 
mainly  upon  the  relative  adsorption  of  the  cation  and  anion 
from  the  solution  present  in  the  capillary  pore.  An  indica- 
tion of  the  magnitude  of  the  charge  on  the  capillary  wall 
may  be  obtained  by  reducing  some  of  the  membrane  ma- 
terial to  a  fine  suspension  which  can  be  placed  in  the  solution 
in  question  and  then  subjected  to  the  influence  of  a  differ- 
ence of  potential  (i.  e.,  the  process  of  cataphoresis) .  The 
direction  and  velocity  of  migration  of  the  particle  indicates 
the  sign  and  magnitude  of  the  charge  upon  it. 

An  application  of  the  above  concept  brings  out  the  fact 
that  a  complete  cell  system  must  exist  in  some  one  of  nine 
different  conditions  of  electrification.  Each  of  the  following 
diagrams  (Fig.  Ill)  represents  a  single  capillary  pore  extending 

i  n  ui 

o 


JL       A 


Fig.  Ill 

through  a  membrane;  in  connection  with  this  pore  there  is 
indicated   also  the  sign   of  the  electrostatic   charge   on   the 


II 

membrane,  the  corresponding  opposite  charge  of  the  liquid 
layer  bathing  the  pore  wall,  and  the  electrical  orientation  of 
the  membrane  system.  In  each  case  the  arrow  on  the  left, 
pointing  upward,  represents  the  direction  of  the  tendency  to 
produce  normal  osmose,  such  for  example,  as  would  be  ob- 
tained with  sugar  solution.  The  arrow  on  the  right  indicates 
the  direction  of  the  superimposed  effect.  The  direction  of 
this  superimposed  effect  may  be  the  same  as,  or  opposite  to, 
the  normal  osmotic  effect.  In  the  latter  case  negative  osmose 
may  result.  The  solution  is  understood  to  be  on  the  upper 
side  of  the  membrane,  and  water  (or  the  more  dilute  solu- 
tion), on  the  lower  side.  The  osmose  due  to  this  superimposed 
effect,  is  assumed  to  be  caused  by  the  passage  of  a  charged 
liquid  layer  along  the  walls  of  the  capillary  pores  of  the  mem- 
brane under  a  driving  force  of  potential  which  acts  as  though 
it  were  set  up  between  the  two  faces  of  the  membrane.1 

If  we  consider  all  the  cases  in  which  it  is  possible  for  the 
cell  systems  to  exist,  we  find,  referring  to  diagrams  in  Fig. 

1  The  term  normal  osmose  has  been  used  throughout  to  designate  that 
process  which  tends  to  produce  an  equilibrium  difference  of  pressure,  of  magni- 
tude expressible  by  the  gas  law  formulations,  when  solution  and  solvent  are 
separated  by  a  membrane  permeable  to  the  solvent  alone.  In  the  present  paper 
absolutely  no  attempt  has  been  made  to  "explain"  the  phenomena  of  normal 
osmose.  It  has  been  assumed  that  a  tendency  to  produce  normal  osmose  does 
exist  within  a  system  whenever  two  aqueous  solutions  of  unequal  concentra- 
tion— or  a  solution  and  water — are  separated  by  a  truly  "semi-permeable" 
membrane.  It  is  also  assumed  that,  in  case  the  membrane  is  not  strictly  semi- 
permeable  but  is,  instead,  permeable  to  solute  as  well  as  solvent,  the  tendency 
to  produce  positive  normal  osmose  still  exists  and  will  continue  to  exist  until 
the  solutions  on  the  two  sides  of  the  membrane  become  of  the  same  concentra- 
tion. Further,  it  has  been  tacitly  assumed  that  the  rate  of  flow  of  liquid  through 
the  membrane  in  normal  osmose  should  be  very  nearly  the  same  with  different 
kinds  of  solutions  which  are  isotonically  equal.  In  those  cases  in  which  the  rate 
of  flow  of  liquid  through  the  membrane  is  different  than  the  rate  obtained  as 
the  result  of  normal  osmose  alone,  it  is  assumed  that  some  superimposed  effect 
is  operative  within  the  system.  The  superimposed  effect  may  act  in  conjunc- 
tion with  the  force  tending  to  produce  normal  positive  osmose,  resulting  thereby 
in  abnormally  great  positive  osmose,  or  the  superimposed  effect  may  act  in  op- 
position to  the  normal  osmotic  tendency  and  may  in  some  cases  even  become  so 
great  as  to  completely  overcome  the  normal  osmotic  effects  and  produce  as  a 
result  a  flow  of  liquid  from  concentrated  to  dilute  solution.  This  we  have  desig- 
nated as  negative  osmose. 


12 


III,  that  in  cases  I,  II,  III,  IV  and  VII,  normal  osmotic  ef- 
fects would  be  obtained;  in  cases  V  and  IX  abnormally  high 
positive  osmose  would  be  produced;  while  in  cases  VI  and 
VIII  an  abnormally  low  osmose  would  be  produced,  which 
osmose  might  even  become  negative. 

Cases  I,  II  and  III  represent  a  membrane  which  is  iso- 
electric  with  the  solution.  This  condition,  even  though  a 
difference  in  potential  might  exist  between  the  faces  of  the 
membrane,  would  produce  normal  osmose. 

Case  I  would  be  obtained  with  a  membrane  electrically 
neutral,  with  a  sugar  solution.  Cases  II  and  III  may  be  con- 
sidered to  exist  when  a  membrane  such  as  porcelain  is  in  con- 
tact with  a  solution  of  an  electrolyte  at  such  concentration 
that  the  membrane  material  is  at  the  iso-electric  point. 

Case  IV  represents  a  membrane  such  as  porcelain  (elec- 
tro-negative) in  a  sugar  solution.  The  membrane  is  negative 
to  the  sugar  solution;  however,  owing  to  the  fact  that  no 
polarization  exists  between  the  two  faces  of  the  membrane, 
only  normal  osmose  would  result. 

Case  V  represents  a  membrane  such  as  porcelain  with 
a  solution  such  as  KNO3;  the  membrane  is  electro-negative 
to  the  solution  and  the  electrical  orientation  of  the  cell  sys- 
tem is  such  that  the  solution  side  is  electro-negative  to  the 
water  side.  This  condition  would  result  in  an  abnormally 
great  positive  osmose. 

Case  VI  exists  when  a  porcelain  membrane  is  in  contact 
with  a  dilute  solution  of  a  base  within  the  cell.  The  mem- 
brane is  negative  to  the  solution,  but  owing  to  selective  ad- 
sorption of  ions  and  also  to  the  more  rapidly  moving  anion, 
the  dilute  solution  side  is  electro-negative  to  the  other  side. 
An  abnormally  small,  or  even  negative  osmose  would  result. 

Case  VII  represents  a  membrane  such  as  aluminium 
oxide  (electro-positive),  with  a  sugar  solution.  The  aluminium 
oxide  is  positive  to  the  sugar  solution,  but  since  no  polariza- 
tion exists  between  the  two  faces  of  the  membrane,  only 
normal  osmose  would  result. 

Case  VIII  exists  with  a  concentrated  solution  of  HC1. 


13 

The  capillary  wall  is  positive  to  the  solution  as  a  whole,  while 
the  water  or  dilute  solution  side  is  electro-positive  to  the 
concentrated  solution  side.  This  condition  would  give  an 
abnormally  low  or  negative  osmose. 

Case  IX  is  obtained  with  an  A1C13  solution.  The  capil- 
lary wall  is  positive  in  respect  to  the  solution,  while  the  dilute 
solution  side  of  the  system  is  electro-negative,  and  would 
therefore  result  in  an  abnormally  great  positive  osmose. 

The  anomalous  osmosis  due  to  the  effect  of  electrolytes  in 
general,  used  singly  or  in  combination,  and  its  relation  to  the 
equilibrium  of  emulsions,  sols,  jellies,  blood  coagulation, 
living  plant  and  animal  cells,  etc.,  may  be  accounted  for  on 
the  basis  above  outlined.  This  explanation  is  further  con- 
firmed by  the  various  data  obtained  in  connection  with  the 
action  of  electrolytes  in  many  different  physiological  and  bio- 
logical systems.  The  same  fundamental  principles  underlie 
all  these  inter-related  phenomena. 

Apparatus  and  Methods 

The  object  of  this  investigation  has  been  to  study  the 
osmotic  effects  produced  by  solutions  of  electrolytes  with  an 
animal  membrane  such  as  gold  beaters  skin,  and  to  ascertain 
whether  any  parallelism  exists  between  the  observed  osmotic 
effects  produced,  and  the  difference  of  potential  associated 
with  the  same  cell  system. 

The  gold  beaters  skin  used  was  of  very  fine  grade  and 
was  of  uniform  texture.  That  we  are  justified  in  considering 
this  membrane  capillary  in  nature  is  evident  from  the  work 
of  Bigelow,29  who  found  that  Poiseuille's  law  for  the  passage 
of  liquids  through  capillary  tubes  applies  to  the  passage  of 
water  through  collodion,  parchment  paper,  and  gold  beater's 
skin. 

It  may  be  well  to  point  out  the  fact  that  gold  beaters 
skin  membranes  are  far  from  being  semi-permeable.  From 
the  beginning  of  an  experiment  to  the  end,  there  is  a  continual 
diffusion  of  solute  from  the  more  concentrated  to  the  more 
dilute  solution.  This  diffusion  of  solute,  which  results  in  a 
change  in  concentration,  will  continue  until  the  solutions 


14 

on  the  two  sides  of  the  membrane  are  of  the  same  concen- 
tration. With  a  membrane  of  this  type,  we  are  unable  to 
even  approach  the  theoretical  maximum  osmotic  pressure 
values.1  What  we  actually  have  obtained  in  this  work,  is 
data  showing  the  rate  of  flow  of  solution  through  the  mem- 
brane. In  some  cases  we  have  measured  also  the  equilibrium 
pressure,  expressed  in  terms  of  hydrostatic  pressure,  of  the 
different  solutions  when  the  rate  of  flow  of  liquid  through 
the  membrane  in  one  direction  was  just  balanced  by  the 
rate  of  flow  of  liquid  in  the  other  direction.  If  the  rate  of 
flow  of  liquid  was  practically  the  same  as  that  of  a  sugar 
solution  of  the  same  concentration,  we  have  considered  the 
rate  of  flow  normal  and  have  designated  the  process  as  nor- 
mal osmose.  If  the  rate  of  flow  of  liquid  is  far  different  from 
that  of  sugar  solution,  we  have  characterized  the  osmose  as 
abnormal  and  the  process  as  one  of  anomalous  osmose.  If 
the  rate  of  flow  of  liquid  was  greater  in  the  direction  of  the 
more  concentrated  solution,  we  have  designated  that  as  a 
positive  osmotic  flow  or  positive  osmose,  while  if  the  rate  of 
flow  was  greater  in  the  direction  of  the  more  dilute  solution, 
we  have  designated  that  as  a  negative  osmotic  flow,  or  nega- 
tive osmose.  It  will  readily  be  appreciated  that  a  comparison 
of  the  rates  of  flow  of  different  solutions  is  in  no  way  an  exact 
means  of  comparing  the  absolute  osmotic  activity  of  the  differ- 
ent solutions.  It  does,  however,  give  us  a  fairly  accurate  in- 
dication of  the  order  of  the  maximum  equilibrium  pressures 
which  may  be  obtained  with  these  solutions.  Furthermore, 
in  those  instances  in  which  the  direction  of  flow  of  solution 
is  opposite  to  that  obtained  in  normal  osmose,  there  seems 
to  be  no  logical  argument  against  the  view  that  some  force 
must  be  operating  in  the  system  in  addition  to  that  tending 
to  produce  positive  osmose.  It  is  for  the  purpose  of  throw- 
ing some  light  on  the  nature  and  source  of  this  additional 
force,  or  superimposed  effect,  that  the  work  of  this  paper  is 
directed. 


1  It  may  be  mentioned  that  this  is  quite  the  type  of  osmotic  membranes 
we  encounter  in  practically  all  living  organisms,  both  animal  and  vegetable. 


Osmotic  experiments  were  carried  out  in  a  cell  of  two 
compartments,  each  half  of  which  consisted  of  a  glass  L-tube 
of  approximately  20  cc  capacity — Fig.  IV.  The  ends  of 
the  L-tubes  in  contact  with  the  membrane  were  ground  to 
make  water-tight  joints.  The  ends  were  covered  with  a 
thin  coating  of  low-melting  paraffin,  which  served  as  a  pro- 
tective cushion  for  the  membrane  when  the  cell  was  set  up. 
The  membrane  was  held  in  place  by  a  piece  of  tightly  fitting 

rubber  tubing,  which,  in  turn, 
was  held  firmly  to  the  paraf- 
fined glass  cell  by  means  of 
tightly  wound  copper  wires, 
the  extensions  of  which  served 
as  legs  to  support  the  cell  in 
an  upright  position.  All  the 
stoppers  in  the  cell  were 
coated  with  paraffin  each  time 
a  cell  was  set  up.  As  a  re- 
sult no  difficulty  was  experi- 
enced from  leakage.  When 
concentrations  of  alkali 
greater  than  o.oi  M  were 
used,  it  was  necessary  to  pro- 
tect the  face  of  the  rubber 
stoppers  with  paraffin.  The 
outlet  tubes,  used  to  measure 
the  osmotic  effects,  were  of 
about  3  mm  internal  diameter. 


Fig.  IV 


At  the  beginning  of  each  experiment  the  cell  was  filled  and 
the  liquids  were  brought  to  the  same  height  in  both  tubes. 
The  temperature  was  kept  at  approximately  20°  C.  Read- 
ings were  taken  every  two  hours  for  twelve  hours,  at 
which  time  the  cells  had  reached  very  nearly  their  maximum 
or  minimum  osmotic  values.  The  main  advantages  of  these 
cells  are  as  follows:  (i)  Any  leak  in  the  cell  is  easily 
detected,  (2)  evaporation  is  practically  eliminated,  (3)  tem- 
perature changes  cause  practically  no  alteration  of  the  hydro- 


i6 


static  pressure  on  the  membrane,  since  a  change  in  tempera- 
ture causes  approximately  the  same  rise  in  each  of  the  outlet 
tubes,  (4)  no  difficulty  is  experienced  in  working  with  solu- 
tions which  must  be  protected  from  atmospheric  contamina- 
tions, since  both  solutions  are  well  enclosed,  (5)  any  change 
in  the  concentration  of  the  two  solutions  due  to  the  dissolving 
of  the  membrane  material  is  practically  the  same,  (6)  correc- 
tions due  to  the  capillarity  are  negligible,  since  the  effects 
are  practically  the  same  in  the  two  outlet  tubes,  (7)  the  whole 
cell  can  easily  be  immersed  in  a  constant  temperature  bath 
when  quantitative  measurements  are  desired. 

Osmose  of  Chloride  Solutions  of  Different  Concentrations  in  a 
One-Compartment  Cell 

In  the  first  series  of  experiments  carried  out,  but  one 
compartment  of  the  above  described  cell  was   used,    Fig.   V. 


Fig.  V 


17 


A  membrane  was  fastened  over  one  end  of  the  glass  L-tube 
and  the  whole  was  suspended  in  a  vessel  of  water,  about  1000 
cc.  With  this  set-up  we  determined  the  osmotic  effect  of  the 
cell  with  a  very  large  volume  of  water  present.  It  was  de- 
sired to  compare  osmotic  effects  obtained  with  large  volumes 
of  water  present  with  those  obtained  when  smaller  volumes 
(about  20  cc)  were  present. 

The  following  tables  contain  the  results  of  the  experi- 
ments on  the  osmose  of  chloride  solutions  of  different  concen- 
trations, and  of  sugar  solutions  of  the  same  concentrations  as 
these,  against  a  large  volume  of  water.  The  data  are  given 
as  rise  in  millimeters  (from  the  original  level  of  the  meniscus). 
The  height  of  the  liquid  in  the  outlet  tubes  was  measured  by 
means  of  a  millimeter  scale  and  estimated  to  0.5  of  a  milli- 
meter. 

TABLE  i 
Concentration  o.oi  M          Solutions  of  chlorides  in  cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1C13 

ThCl4 

Sugar 

0 

0 

0 

0 

0 

o 

O 

0 

0 

2 

2 

i-5 

3 

6 

6 

21 

79 

2 

4 

4 

3 

5 

ii 

"•5 

49 

153 

4 

6 

5 

5 

6-5 

16 

17 

81 

230 

6 

8 

6 

6-5 

7 

19 

21 

H3 

297 

8 

10 

7 

8 

8 

21 

25 

150 

365 

ii 

12 

7 

8 

9 

22.5 

27 

.   i87 

403 

12 

TABLE  2 
Concentration  0.02  M          Solutions  of  chlorides  in  cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1C13 

ThCl4 

Sugar 

0 

0 

0 

0 

0 

0 

0 

0 

0 

2 

2-5 

3 

2-5 

3 

2 

61 

9i 

7 

4 

4 

5 

3-5 

8 

8 

133 

202 

ii 

6 

5 

7 

5 

10.5 

ii 

213 

315 

15 

8 

6 

8-5 

6-5 

16 

17 

270 

403 

18 

10 

6-5 

9 

8-5 

25 

27 

345 

509 

21 

12 

7-5 

9 

10 

30 

35 

420 

564 

23 

i8 


TABLE  3 
Concentration  0.05  M  Solutions  of  chlorides  in  cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1C13 

ThCl4 

Sugar 

0 

0 

O 

0 

0 

O 

o 

o 

0 

2 

2 

2 

2.5 

8 

9 

93 

131 

12 

4 

4 

4 

4 

15 

18 

198 

325 

20 

6 

5 

5-5 

5-5 

22 

23-5 

285 

456 

30 

8 

6 

7 

7 

28 

29 

367 

5H 

38 

10 

7 

7-5 

9 

32 

33 

468 

579 

46 

12 

8-5 

10 

ii 

36 

38 

550 

660 

51 

Concentration  o.  i  M 


Solutions  of  chlorides  in  cells 


Time 
(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1C13 

ThCl4 

Sugar 

0 

0 

0 

0 

0 

0 

0 

0 

0 

2 

3 

3-5 

3-5 

20 

23 

137 

201 

15 

4 

5-5 

6 

6-5 

35 

32 

281 

461 

35 

6 

8 

8-5 

9 

45 

45 

390 

657 

54 

8 

10 

10 

10 

50 

55 

494 

777 

69 

10 

ii 

n-5 

12 

55 

65 

615 

891 

84 

12 

12 

12.5 

H 

58 

75 

738 

977 

99 

Osmose  of  0.05  M  Chlorides  in  Two-Compartment  Cells 

This  set  of  experiments  was  made  with  the  volumes  of  solu- 
tion and  solvent  on  opposite  sides  of  the  membrane,  as  nearly 
equal  as  possible.  This  was  done,  in  contrast  to  the  condi- 
tions in  the  previous  experiments  in  which  the  volume  of  solu- 
tion and  solvent  were  made  very  unequal,  in  order  to  study 
the  influence  of  the  relative  volumes  of  solution  and  water 
on  the  osmotic  effect.  For  these  experiments,  likewise  for 
those  in  which  the  effect  of  acid  and  alkali  was  studied,  as 
also  for  those  in  which  measurements  were  made  of  the  E. 
M.  F.,  the  two-compartment  type  of  osmotic  cell  previously 
described  was  employed.  Using  this  type  of  cell,  experi- 
ments were  made  to  determine  the  osmose  of  o .  05  M  chlorides. 
The  results  thus  obtained  are  given  in  the  following  table: 


TABLE  5 

Solutions  of  chlorides  in  two- 
Concentration  0.05  M  compartment  cells 


Time 
(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

Aids 

ThCl4 

0 

o 

o 

o 

O 

0 

0 

0 

2 

9 

3-5 

5-5 

27 

42.5 

112.5 

9i 

4 

20 

8-5 

10.5 

42.5 

66.5 

129 

112.5 

6 

25 

15 

19 

55 

84 

152-5 

150 

8 

28 

21 

27 

62.5 

97-5 

H7-5 

1  66 

10 

29 

27-5 

3i 

61 

107 

142 

170 

12 

29 

31 

36 

61 

112 

137 

169 

The  data  contained  in  the  preceding  tables  show  that: 

1.  The  order  of  osmose  of  the  several  salt  solutions  was 
the  same  with  the  double  cell  as  with  the  single  type  of  cell. 

2.  The  osmose  of  the  salt  solutions  of  univalent  and  di- 
valent cations  was  decidedly  greater  in  the  two-compartment 
cell  than  in  the  single  cell. 

3.  On    the    other    hand,    the    salt    solutions    containing 
polyvalent  cations,  as  aluminium  and  thorium,  gave  decidedly 
smaller  effects  in  the  two-compartment  cell  than  in  the  single 
cell. 

The  Osmose  of  Acid  and  Alkali  Against  Water 

In  these  experiments  nitric  acid  and  sodium  hydroxide 
were  employed.  Carbon  dioxide-free  water  was  used  to  make 
the  solutions  of  alkali.  The  outlet  tubes  were  closed  with 
very  small  soda  lime  tubes  to  prevent  the  adsorption  of  carbon 
dioxide  from  the  atmosphere. 

A  positive  effect  signifies  a  flow  of  liquid  toward  the  side 
of  the  membrane  in  contact  with  the  electrolyte,  and  a  nega- 
tive effect,  indicated  as  ( — •),  signifies  a  passage  of  liquid  in 
the  opposite  direction.  The  osmose  is  expressed  in  terms  of 
rise  in  mms  of  solution,  which  is  half  the  actual  hydrostatic 
pressure,  or  half  the  difference  in  level  of  the  liquids  in  the  two 
outlet  tubes. 

Concentrations   of   both   acid   and   alkali   varying   from 


2O 


o.oooi  M  to  0.5  M  were  employed,  and  the  results  of  the 
tests  are  shown  in  Tables  6  and  7. 

TABLE  6 
The  Osmose  of  Nitric  Acid 


Time 

(hrs.) 

o.oooi  M 

o.ooi  M 

o.oi  M 

o.i  M 

0.2  M 

0.5  M 

o 

0 

0 

0 

0 

0 

o 

2 

o 

o 

3-5 

-i-5 

—7-5 

-14-5 

4 

0.3 

0-5 

6-5 

2 

—  12 

22 

6 

0-5 

i 

9-5 

—2.5 

-H-5 

—26 

8 

0.7 

i-5 

"•5 

—2.7 

—  15-5 

—2/.5 

10 

i 

2 

13 

—2-5 

—  16 

—28 

12 

i 

2-5 

H-5 

2 

-16.5 

-28.5 

From  Table  6  it  may  be  pointed  out  that: 

1.  Nitric  acid  gives  both  positive  and  negative  osmose, 
depending  on  the  concentration  of  the  acid  employed. 

2.  The  osmose  is  positive  at  concentrations  of  o.oi  M  or 
less,  and  negative  at  higher  concentrations. 

3.  The  osmose  increases  from  o.oooi  M  to  o.oi  M  as 
the  concentration  increases,  but  at  o .  i  M  concentration  the 
osmose  becomes  slightly  negative,  and  continues  to  become 
increasingly  negative  as  the  concentration  of  the  acid  is  in- 
creased. 

TABLE  7 
The  Osmose  of  Sodium  Hydroxide 


Time 
(hrs.) 

o.oooi  M 

o.ooi  M 

o.oi  M 

o.i  M 

0.2  M 

0.5  M 

O 

0 

0 

0 

0 

0 

0 

2 

0 

i-5 

I 

0 

—4 

—5 

4 

0-5 

2 

2 

o 

—3-5 

7 

6 

0-5 

2 

3 

0 

—2-5 

—7-5 

8 

i 

2 

4 

0 

2 

—6 

10 

i-5 

3 

5 

0.2 

2 

—5-5 

12 

i-5 

3 

5 

I 

2 

—5-5 

Table  7  shows  that: 

i.  Sodium  hydroxide  also  gives  both  positive  and  nega- 


tive osmose. 


21 


2.  The  osmose  is  distinctly  positive  at  concentrations  of 
o.o i  M  or  less,  but  seems  to  be  practically  zero  at  o.  i  M  con- 
centration, and  becomes  increasingly  negative  as  the  concen- 
tration^ increases . 

It  is  a  peculiar  and  interesting  fact  that  the  turning  point 
for  both  the  acid  and  alkali  is  at  about  the  same  order  of  con- 
centration, namely  o.oi  M  to  0.02  M.  (See  Fig.  VI.) 


Fig.  vi 

_In  this  same  connection  it  may  be  noted  that  Bartell 
and  Hocker,30  in  their  work  with  porous  porcelain  mem- 
branes, make  mention  of  a  similar  turning  point  in  the  case  of 
hydrochloric  acid  and  sodium  hydroxide,  but  they  did  not  ob- 
serve negative  osmose  with  the  concentrations  of  acid  used. 

Measurement  of  Cell  Potential 

The  relation  of  osmose  to  cell  potential  was  studied  by 
measuring  the  potential  of  the  cell  system  when  the  cells 
were  set  up  precisely  as  when  measurements  of  osmose  were 
to  be  made.  These  potential  measurements  were  made  by 
the  compensation  method,  using  calomel  electrodes,  a  Wolff 
potentiometer,  and  a  sensitive  galvanometer.  Two  modified 
Hulett  batteries  connected  in  series  served  as  a  source  of  poten- 
tial for  the  external  balancing  current.  These  batteries 


22 


maintained  a  very  good  constancy.  One  electrode  was  brought 
in  direct  contact  with  the  solution  and  the  other  electrode 
in  similar  contact  with  the  water,  giving  the  chain:  Hg- 
Hg2Cl2-o.i  M  KCl-solution-membrane-water-o.i  M  KC1- 
Hg2Clo-Hg.  In  the  case  of  electrolytes  used  in  combination, 
the  chain  was:  Hg-Hg2Cl2-o.i  M  KCl-solution  A-membrane- 
solution  B-o.i  M  KCl-Hg2Cl2-Hg.  Only  the  initial  constant 
values  were  utilized  since,  as  pointed  out  by  Bayliss  in  his 
work  with  parchment  paper,31  they  seem  to  be  the  more  re- 
liable for  comparative  data.  However,  a  sufficient  number 
of  time  measurements  were  taken  to  ascertain  that  the  E.  M.  F. 
steadily  falls  after  the  cell  has  been  set  up  for  a  time.  This 
is  due  probably  to  diffusion  of  the  electrolyte  through  the 
membrane,  causing  a  change  in  concentration  of  the  solutions 
bathing  the  faces  of  the  membrane. 

The  Electromotive  Force  of  0.05  M  Chlorides  vs.  H20 

These  and  subsequent  electromotive  force  measurements 
were  made  in  an  endeavor  to  ascertain  whether  there  was  any 
relation  between  the  osmotic  effect  produced  and  the  electro- 
motive force  of  the  same  cell  system.  The  measurements 
were  carried  out  as  previously  described  and  are  contained 
in  the  following  table.  The  results  given  are  the  averages 
of  two  or  more  measurements,  none  of  which  varied  more 
than  two  millivolts  from  the  average  value  given.  All  the 
E.  M.  F.  measurements  were  made  within  5  minutes  after 
the  cell  was  set  up. 

TABLE;  8 
E.  M.  F.  of  0.05  M  Chlorides  against  H2O 


Solution 

Potential 
Solution  side 

Solution 

Potential 
Solution  side 

KC1 
NaCl 
LiCl 
BaCl2 

+0.002 
+0.015 
+0.046 
+0.050 

MgCl2 
A1C13 
ThCl4 

+0.060 
+0.067 
+0.070 

TABLE  9 
The  E.  M.  F.  of  HNO3  and  NaOH  against  H2O 


Concentration 
HN03 

Potential 
Solution  side 

Concentration 
NaOH 

Potential 
Solution  side 

o.ooi  M 
o.oi  M 
o.i  M 

—  0.050 
—  0.092 
—  o.  no 

O.OOI  M 
o.oi  M 
o.i  M 

+O.OI8 
+0.040 
+0.059 

Summary  of  Results  and  Conclusions 

i.  The  principal  relationships  found  have  been  brought 
together  in  the  following  table: 


Solution 

Osmose 

Sign  of 
Potential 
Solution 
side 

Sign  of 
liquid 
layer 

Osmotic 
Tendency 

Single 
cell 
(12  hrs.) 

Double 
cell 

(12  hrs.) 

0.05  M  Sugar 



51 

0.000 

Normal  (Positive) 

0.05  M  KC1 

29 

8-5 

+  O.OO2 

+ 

Negative 

0.05  M  NaCl 

31 

IO 

+  0.015 

+ 

Negative 

0.05  M  LiCl 

36 

I  I 

+0.046 

+ 

Negative 

0.05  M  BaCl2 

61 

36 

+  0.050 

+ 

Negative 

0.05  M  MgCl2 

I  12 

38 

+  0.060 

+ 

Negative 

o.  05  M  A1C13 

137 

550 

+  0.067 

— 

(Abnormally    posi- 

tive) 

0.05  M  ThCl4 

169 

660 

+0.070 

— 

(Abnormally    posi- 

tive) 

o.ooi  MHNO3 



2-5 

—  0.050 

+ 

(Abnormally    posi- 

tive) 

o.oi  M  HNO3 



H-5 

—  o  .  092 

— 

(Probably    near 

turning  point) 

o.i  MHN03 



2.0 

—  o.  no 

— 

Negative 

o.ooi  M  NaOH 



3 

+0.018 

+ 

Negative 

o.oi  M  NaOH 



5 

+0.040 

+ 

Negative 

o.i  MNaOH 



—  i 

+0.059 

+ 

Negative 

2.  The  osmose  of  sugar  solutions  indicate  that  the  rate 
of  osmose  is  very  nearly  proportional  to  the  concentration  of 
the  solution. 

3.  It  is  noted  that  the  direction  and  magnitude  of  flow 
of  solution  is,  in  practically  every  case,  that  which  we  would 
predict   from  the  postulates   above   stated.     If  the  solution 


24 

side  of  the  membrane  system  is  of  the  same  electrical  sign  as 
the  capillary  liquid  layer  the  resulting  osmose  will  be  ab- 
normally low,  or  negative;  whereas  if  these  parts  of  the  sys- 
tem are  of  opposite  sign  the  resulting  osmose  will  be  abnormally 
high. 

4.  With  salts  of  univalent  and  divalent  cations  the  super- 
imposed effect  is  found  to  work  in  opposition  to  normal  osmose, 
with  the  result  that  the  observed  rate  of  osmose  is  less  than 
normal. 

5.  With   salts   of   Al   and   Th   the   superimposed   effect 
works  in  conjunction  with  the  normal  osmose  and  the  result 
is  an  abnormally  great  osmose. 

6.  Increase  in  concentration  causes  but  slight  increase 
in  osmose  of  solutions  of  univalent  cations,  a  marked  increase 
in  osmose  of  solutions  of  divalent  cations  and  a  decidedly 
greater  increase  in  osmose  of  solutions  of  trivalent  and  quadri- 
valent cations.      A  logical  explanation,  for  the  facts  just  men- 
tioned, seems  to  be  that  with  dilute  solutions  of  univalent  and 
divalent  cations,  the  charge  of  the  membrane  against  the  solu- 
tion is  at  all  times  electro-negative  which  tends  to  produce 
an  abnormally  low  osmose.     In  the  case  of  the  solutions  of 
divalent  cations  there  is  a  marked  tendency  to  neutralize 
the  negative  charge  of  the  membrane,  with  the  result  that 
with    the    more    concentrated    solutions    the   membrane    ap- 
proaches the  iso-electric  point  and  osmose  now  approaches 
the  normal  rate.     In  the  case  of  solutions  of  trivalent  and 
quadrivalent  cations,  the  sign  of  the  membrane  is  electro- 
positive, even  with  the  very  dilute  solutions ;  this  results  in  an 
abnormally  great  positive  osmose  in  every  case. 

7.  With  the  two-compartment  cells,  the  concentrations 
of  the  solutions  on  the  two  sides  of  the  membrane  are  much 
more  nearly  equal  than  in  the  one-compartment  cell.     This 
is  due  to  the  small  initial  water  volume,  with  the  result  that 
the  K.  M.  F.  of  the  membrane  system  is,  in  this  case,  much 
less  than  in  the  case  of  the  one-compartment  cell.     Owing  to 
the  smaller  potential  difference  between  the  two  faces  of  the 
membrane,  the  resulting  osmose  is  in  all  cases  more  nearly 


25 

normal.  In  the  case  of  the  solutions  of  imivalent  cations, 
there  exists  a  lesser  tendency  toward  negative  osmose,  whereas 
in  the  case  of  solutions  of  polyvalent  cations,  as  Al  and  Th, 
there  exists  a  lesser  tendency  for  an  abnormally  great  posi- 
tive osmose. 

8.  In  the  case  of  dilute  acid  the  tendency  is  toward  an 
abnormally    great    positive    osmose.     As    the    concentration 
of  acid  is  increased,  the  sign  of  the  capillary  system  is  changed 
(reversed),  and  the  osmotic  tendency  passes  from  abnormally 
great  positive  to  normal,  then  to  abnormally  small,  and  finally 
to  negative  osmose. 

9.  In  the  case  of  sodium  hydroxide,  a  negative  tendency 
persists  throughout.     At  the  higher  concentrations  the  elec- 
trical factors  of  the  system  are  such  that  negative  osmose 
results. 

10.  Work  with  porcelain  membranes  showed  somewhat 
similar  results  for  the  osmotic  behavior  of  acids  and  alkalis. 
In  some  investigations  it  has  been  found  that  with  certain 
concentrations    of    acid    or    alkali,    (approx.    o.oi  M    cone.) 
positive  osmose  may  be  of  a  very  considerable  magnitude, 
whereas  at  still  higher  concentration  of  acid  or  alkali,  nega- 
tive  osmose   may   result.     At   higher   concentrations,    about 
10  M  cone.,  positive  osmose  again  results.32     That  is,  the  curve 
in  Fig.  VI  for  acid  against  water  comes  above  the  concentra- 
tion axis  again  and  thus  forms  practically  a  sine  curve. 

All  these  facts  coincide  with  many  physiological  observa- 
tions which  up  to  the  present  time  have  received  no  satis- 
factory explanation. 

In  our  previous  studies  of  the  relation  of  osmose  of  solu- 
tions of  electrolytes  to  the  electrical  states  of  the  membrane 
system,  we  concluded  that  the  nature  and  magnitude  of  the 
resulting  osmose  was  dependent  largely  upon  two  factors: 

(1)  the  electrical  orientation  of  the  membrane  system,  and 

(2)  the  electrical  orientation  of  the  capillary  wall  system. 
The  four  conditions  responsible  for  abnormal  osmose  may  be 
represented  by  the  following  diagrams,  Fig.  VII. 


26 


B 


D 


Fig.  VII. 

With  conditions  represented  in  A  and  D,  an  abnormally 
great  positive  osmose  would  be  obtained;  while  with  condi- 
tions represented  in  B  and  C,  an  abnormally  low,  or  even 
negative,  osmose  would  result. 

Gold  beaters  skin  in  pure  water  is  electro-negative  to 
the  water.  With  dilute  salt  solutions  of  univalent  cations, 
the  solution  side  of  the  membrane  system  is  electro-positive 
to  the  other  side  (case  B),  which  should  give  as  a  result  a 
tendency  to  produce  an  abnormally  low  osmose.  In  our  ex- 
perimental work  we  have  found  that  this  prediction  correctly 
represents  the  facts. 

With  salt  solutions  of  polyvalent  cations  as  aluminium 
and  thorium,  the  membrane  becomes  electro-positive  to  the 
solution.  The  solution  side  of  the  membrane  is  electro-posi- 
tive (case  D).  The  resulting  osmose  should  be  abnormally 
positive.  The  experimental  results  were  entirely  in  accord 
with  this  prediction. 

It  is  well  known  that  small  amounts  of  acids  or  bases 
play  an  important  role  in  adsorption,  and  that  comparatively 
small  amounts  of  these  substances  tend  to  alter  greatly  the 
sign  of  the  charge  of  any  adsorbing  materials  placed  in  such 
solutions. 

It  was  our  aim  in  the  present  investigation  to  study  the 
effect  of  the  presence  of  different  concentrations  of  acids  and 
bases  upon  the  osmose  of  different  salt  solutions.  If  our 
fundamental  hypothesis  is  correct,  we  should  be  able,  by 
altering  the  sign  of  the  charge  of  the  membrane  by  having 
present  acids  or  bases,  to  greatly  alter  the  osmotic  effects  of 
the  different  salt  solutions.  For  example,  those  salt  solutions 
which  show  an  abnormally  great  osmose  in  neutral  solution 


27 


should  be  caused  to  show  an  abnormally  low  or  even  negative 
osmose  when  the  electrical  sign  of  the  system  is  properly 
altered  by  the  presence  of  acid  or  alkali.  Solutions  of  chlorides 
of  K,  Na,  Li,  Ba,  Mg,  Al  and  Th  (the  same  salts  that  were 
used  in  our  earlier  investigation),  of  0.05  concentration,  were 
used. 

Three  series  of  experiments  were  run  in  which  were  used 
both  HNOs  and  NaOH  solutions  of  different  concentrations. 
The  acid  or  alkali  was  used  (1)  throughout  the  cell  system, 
(2)  on  the  solution  side  of  the  membrane  with  distilled  water 
on  the  opposite  side,  and  (3)  on  the  side  of  the  membrane 
opposite  to  that  of  the  solution. 

The  apparatus  and  methods  used  were  the  same  as  those 
described  in  the  previous  paper.  The  results  obtained  are 
shown  in  the  following  tables. 

TABLE  1 

Concentration   of   0 . 05  M.     Solutions   of   Chlorides   in   Two-Com- 
partment Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

Bad* 

MgCl2 

A1C13 

ThCl4 

0 

0 

0 

0 

0 

0 

0 

0 

2 

9 

3.5 

5.5 

27 

42.5 

112.5 

91 

4 

20 

8.5 

10.5 

42.5 

66.5 

129 

112.5 

6 

25 

15 

19 

55 

84 

152.5 

150 

8 

28 

21 

27 

62.5 

97.5 

147.5 

166 

10 

29 

27.5 

31 

61 

107 

142 

170 

12 

29 

31 

36 

61 

112 

137 

169 

TABLE  2 

Acid  throughout  the  Cell  System 
Concentration  of  Acid  0.0001  M.     0.05M  Chloride  in  Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

Aid. 

ThCU 

0 

0 

0 

0 

0 

0 

0 

0 

2 

9.5 

12.5 

16 

22.5 

64 

72 

42 

4 

16 

21 

29.5 

36 

112 

90 

49 

8 

20 

27.5 

39 

44.5 

142 

81 

40 

8 

22.5 

33 

42 

49 

162 

72 

33 

10 

25 

34.5 

44 

55.5 

174 

56 

27 

12 

27 

37 

46 

60 

182 

46 

24 

28 


TABLE  3 

Acid  throughout  the  Cell  System 
Concentration  of  Acid  0.001  M.     Solutions  of  Chlorides  in  Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1C1S 

ThCU 

0 

0 

0 

0 

0 

0 

0 

0 

2 

17 

29.5 

35 

82 

116 

105 

14 

4 

32 

33 

71 

150 

204 

112 

12 

6 

43.5 

44 

91 

202 

306 

100 

10.5 

8 

50 

54 

108 

251 

380 

92 

8 

10 

53 

57 

118 

271 

414 

81 

4.5 

12 

55 

68 

121 

312 

466 

71 

3 

TABLE  4 

Acid  throughout  the  Cell  System 

Concentration  of  Acid  0.01  M.     0.05  M  Solutions  of  Chlorides  in 

Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1CU 

ThCU 

0 

0 

0 

0 

0 

0 

0 

0 

2 

14 

26.5 

32 

49 

93.5 

61 

11 

4 

23.5 

35 

51 

99 

17S 

50 

9 

6 

29 

38 

60.5 

144 

270 

40 

7 

8 

34.5 

40 

62 

173 

336 

35 

5 

10 

38 

46 

52 

208 

392 

29 

3 

12 

42 

48- 

50 

227 

429 

23 

3 

TABLE  5 

Acid  throughout  the  Cell  System 

Concentration  of  Acid  0 . 1  M.     0 . 05  M  Solutions  of  Chlorides  in 

Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1C13 

ThCU 

0 

0 

0 

0 

0 

0 

0 

0 

2 

3.5 

7.5 

9.5 

25 

26.5 

21 

6.5 

4 

5.5 

10 

12.5 

44 

43 

36 

5 

6 

7 

16 

19 

62 

63 

31 

4 

8 

9 

19 

26.5 

72 

78 

25 

1 

10 

10 

20.5 

30 

SI 

93 

21.5 

0 

12 

10 

22.5 

31.5 

91 

105 

16 

0 

29 


TABLE  6 

Acid  on  Solution  Side ;  Distilled  Water  on  Other  Side 
Concentration  of  Acid  0.0001  M.     0.05  M  Solutions  of  Chlorides  in 

Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1C13 

ThCl4 

0 

0 

0 

0 

•o 

0 

0 

0 

2 

7 

8 

10.5 

23 

41 

71 

80 

4 

11 

17 

29 

38 

102 

1  55 

170 

6 

13  ' 

20 

44 

37 

155 

213 

250 

8 

12 

17.5 

54 

26 

195 

247 

275 

10 

11 

14 

66 

19 

227 

256 

282 

12 

9 

9.5 

72 

12 

242 

252 

270 

TABLE  7 

Acid  on  Solution  Side;  Distilled  Water  on  Other  Side 
Concentration  of  Acid  0.001  M.     0.05  M  Solutions  of  Chlorides  in 

Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2  . 

A1C1.3 

ThCl4 

0 

0 

0 

0 

0 

0 

0 

0 

2 

22 

31 

36 

52 

96 

162 

175 

4 

1C) 

53 

72 

49 

196 

291 

300 

6 

58 

69 

103 

37 

285 

343 

350 

8 

68 

76 

121 

21 

359 

353 

376 

10 

71 

si 

135 

13 

429 

:M7 

355 

12 

71 

80 

144 

8 

483 

334 

330 

TABLE  8 

Acid  on  Solution  Side;  Distilled  Water  on  Other  Side 
Concentration  of  Acid  0.01  M.     0.05  M  Solutions  of  Chlorides  in 

Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1C18 

ThCU 

0 

0 

0 

0 

0 

0 

0 

0 

2 

20 

25 

29 

75 

75 

120 

1  12 

4 

37 

46 

61 

61 

163 

240 

265 

8 

54 

59 

85 

57 

246 

:«7 

374 

8 

61 

67 

110 

43 

316 

392 

422 

10 

67 

69 

1  !>:> 

30 

380 

432 

461 

12 

70 

71 

132 

18 

436 

455 

500 

TABLE  9 

Acid  on  Solution  Side ;  Distilled  Water  on  Other  Side 
Concentration  of  Acid  0.02  M.     0.05  M  Solutions  of  Chlorides  in 

Cells 


Time 
(hrs.) 

KC1 

NaCl 

LiCl 

BaClo 

MgCl2 

A1CU 

ThCl4 

0 

0 

0 

0 

0 

0 

0 

0 

2 

18 

25 

26 

61 

63 

77 

98 

4 

31 

38 

51 

111 

133 

156 

240 

6 

41 

44 

70 

156 

190 

232 

280 

8 

50 

54 

85 

189 

215 

289 

340 

10 

56 

55 

99 

235 

263 

333 

400 

12 

51 

62 

109 

252 

287 

274 

445 

TABLE  10 

Acid  on  Solution  Side;  Distilled  Water  on  Other  Side 
Concentration  of  Acid  0 . 05  M.     0 . 05  M  Solutions  of  Chlorides  in 

Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1C13 

ThCl4 

0 

0 

0 

0 

0 

0 

0 

0 

2 

8 

13 

14 

35 

43 

101 

105 

4 

13.5 

24 

27 

81 

92 

216 

228 

6 

16.5 

36 

37 

116 

130 

244 

262 

8 

15.5 

39 

41 

138 

151 

275 

294 

10 

15.5 

44 

47.5 

157 

167 

306 

324 

12 

15.5 

48 

51 

172 

-    184 

340 

360 

TABLE  11 

Acid  on  Solution  Side ;  Distilled  Water  on  Other  Side 
Concentration  of  Acid  0 . 1  M.     0 . 05  M  Solutions  of  Chlorides  in 

Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

AlCla 

ThCl4 

0 

0 

0 

0 

0 

0 

0 

0 

2 

4 

9 

9.5 

25 

24 

41 

54 

4 

7 

15 

17 

44 

42 

78 

86 

6 

8.5 

21 

23 

62 

62 

124 

142 

8 

10 

25 

28 

74 

76 

158 

186 

10 

10.5 

28 

32 

86 

90 

193 

245 

12 

11.5 

30 

35.5 

95 

100 

221 

,282 

TABLE  12 

Acid  on  Solution  Side;  Distilled  Water  on  Other  Side 
Concentration  of  Acid  0.2  M.     0 . 05  M  Solutions  of  Chlorides  in 

Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

Aldi 

ThCU 

0 

0 

0 

0 

0 

0 

0 

0 

2 

1.5 

4 

4 

10 

10 

19.5 

24 

4 

2.5 

7 

8 

20 

20 

39 

48 

6 

3 

11 

12.5 

30 

32 

70 

88 

8 

3.5 

12.5 

13.5 

35 

38 

84 

116 

10 

4 

13 

17 

42 

46.5 

107 

132 

12 

3.5 

15 

19 

46.5 

52.5 

122 

146 

TABLE  13 

Acid  on  One  Side ;  Solution  on  the  Other  Side 

Concentration  of  Acid  0.0001  M.    0.05  M  Solutions  of  Chlorides  in 

Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

AlCla 

ThCU 

0 

0 

0 

0 

0 

0 

0 

0 

2 

9.5 

7.5 

19.5 

39 

49 

69 

25 

4 

13 

12 

33.5 

56.5 

98 

140 

17 

6 

15.5 

14.5 

38 

63.5 

124 

70 

14 

8 

17 

16 

41 

64 

136 

15 

10 

10 

18 

19 

41 

62 

>142 

15 

7 

12 

18 

22 

41 

59 

141 

15 

4 

TABLE  14 

Acid  on  One  Side;  Solution  on  the  Other  Side 

Concentration  of  Acid  0.001  M.     0.05  M  Solutions  of  Chlorides  in 

Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

Aids 

ThCl4 

0 

0 

0 

0 

0 

0 

0 

0 

2 

24 

29 

31 

76 

22 

80 

67 

4 

42 

59 

53 

80 

30 

144 

87 

6 

54 

78 

68 

84 

29 

152 

137 

8 

61 

94 

87 

64 

27 

162 

125 

10 

64 

104 

102 

54 

26 

167 

110 

12 

66 

109 

114 

49 

25 

167 

90 

TABLE  15 

Acid  on  One  Side;  Solution  on  the  Other  Side 

Concentration  of  Acid  0.01  M.     0.05  M  Solutions  of  Chlorides  in 

Cells 


Time 
(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1C1, 

ThCl4 

0 

0 

0 

0 

0 

0 

0 

0 

2 

28 

33.5 

35 

81 

11.5 

147 

275 

4 

48 

66 

71 

92 

12.5 

200 

350 

6 

61 

89 

90 

104 

11 

222 

425 

8 

69 

106 

113 

80 

11 

222 

500 

10 

73 

121 

123 

72 

11 

222 

525 

12 

75 

130 

133 

63 

11 

222 

540 

16 

Acid  on  One  Side ;  Solution  on  the  Other  Side 

Concentration  of  Acid  0.1M.     0.05M  Solutions  of  Chlorides  in 

Cells 


Time 
(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl-2 

A1C18 

ThCl4 

0 

0 

0 

0 

0 

0 

0 

0 

2 

2 

20 

24 

45 

47.5 

51 

220 

4 

2 

27 

38.5 

54 

60 

65 

310 

6 

2 

30 

44 

60 

68 

71 

340 

8 

2 

28 

47 

48 

68 

74 

355 

10 

2 

26 

47 

45 

66 

76 

350 

12 

2 

26 

47 

45 

66 

75 

350 

TABLE  17 

Alkali  throughout  the  Cell 

Concentration  of  Alkali  0.0001  M.     0.05  M  Solutions  of  Chlorides 

in  Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

A1C13 

ThCl4 

0 

0 

0 

0 

0 

0 

"o 

0 

2 

2 

4 

5 

13 

15 

97 

101 

4 

3 

5 

7 

24 

23 

176 

186 

6 

4 

7 

11 

29 

27 

225 

240 

8 

6 

9 

14 

33 

32 

256 

262 

10 

9 

12 

17 

33 

35 

280 

290 

12 

11 

14 

18 

33 

35 

285 

310 

33 


TABLE  18 

Alkali  throughout  the  Cell 

Concentration  of  Alkali  0 . 001  M.     0 . 05  M  Solutions  of  Chlorides  in 

Cells 


Time 

(hrs.) 

KC1 

NaCl 

LiCl 

BaCl2 

MgCl2 

ALC13 

ThCU 

0 

0 

0 

0 

0 

0 

0 

0 

2 

2.5 

10 

11 

7 

8 

35 

85 

4 

4.5 

17 

20 

9.5 

11 

40 

90 

6 

7 

22 

25 

10.5 

13 

39 

65 

8 

7.5 

25 

28 

9.5 

17 

39 

44 

10 

9 

27 

30 

9.5 

16 

32 

40 

12 

11 

29 

33 

9.5 

16 

32 

38 

TABLE  19 

Alkali  throughout  the  Cell 
Cone,  of  Alkali  0.01  M.     0.05  M  Solutions  of  Chlorides  in  Cells 


Time 

(hrs.) 

KC1 

NaCl 

UC1 

0 

0 

0 

0 

•2 

2 

3 

3.5 

4 

3 

4 

5 

C) 

4 

6 

7 

8 

6 

8 

9 

10 

7 

12 

14 

12 

7 

15 

IS 

TABLE  20 

Alkali  throughout  the  Cell 
Cone,  of  Alkali  0. 1  M.     0.05  M  Solutions  of  Chlorides  in  Cells 


Time 

(hrs.) 

KCl 

NaCl 

LiCl 

0 

0 

0 

0 

2 

0 

2 

3 

4 

i 

4 

4.5 

<i 

2 

5 

(> 

8 

2 

5 

7 

10 

3 

5 

9 

12 

4 

5 

10 

34 


•^  d  co 

1 

CO 

000 

• 

o 

o 

o  o  o 

d 

+  +  1 

H 

+ 

tO  O  CO 

^ 

CO 

rH 

o  o  o 

g 

o 

0 

odd 

(j 

!    ^ 

d 

+  +  1 

1 

+ 

rH    O    CO 

C^  tS*  *-O 

o 

GO 

§88 

bJO 

O 

CO 

O 

o 

be 

O  O  O 

a 

O 

^ 

'fl 

i>  to  o 

2 

00 

00  CO  tO 

f 

o 

CO 
CM 

o 

odd 

hM 

c3 

PQ 

d 

+  +  1 

6 

O  rfi  <M 

w  ^ 

I-J    c^} 

^    O   r- 

§88 

H  1 

0 

r^    0   C 

O  O  O 

O  O  O 

+  +  1 

jd 

o  d  o 

»O  O  00 
CO  CM  (M 

O 

,000 

rH    O    O 

o  o  o 

S 

O 

<3 

sM 

odd 

++  1 

o 

d 

* 

000 

+•+4 

IS 

rH    O   10 

O  O  to 

(Mr-nO 

000 

a 

0 

odd 

tii 

h^ 

O  O  O 

+  +  1 

+  +  + 

*** 

1 

^^ 

8rH 

•g 

0  —  i  ^ 

O   rH 

i 

O    O    rH 

odd 

a 

o 

o  o  d 

U 

35 

The  Electromotive  Force  of  0.05  M  Chlorides  with  Nitric 
Acid  and  with  Sodium  Hydroxide  throughout  the  Syetem. — 
In  order  to  study  the  effect  of  the  presence  of  acid  on  the 
E.  M.  F.  of  the  neutral  salt  solutions,  and  to  compare  this 
effect  with  the  effect  the  acid  exercised  on  the  osmose  of  the 
same  salt  solutions,  measurements  were  made  of  the  cell 
potential  of  0 . 05  M  chlorides  when  different  concentrations 
of  nitric  acid  were  used  throughout  the  system.  The  con- 
centrations of  acid  used  were  0 .001  M,  0 .01  M,  and  0 . 1  M. 

A  study  similar  to  that  made  with  nitric  acid  was  made 
with  sodium  hydroxide.  The  following  tables  give  only  the 
results  obtained  when  either  the  acid  or  alkali  was  present 
throughout  the  entire  system.  The  -f  or  —  sign  indicates 
the  sign  of  potential  on  the  solution  side  of  the  membrane. 
Summary  of  Results 

Summary  of  Results. — A  summary  of  the  results  obtained 
when  acid  or  alkali  are  present  throughout  the  cell  system 
is  best  shown  by  the  curves  in  Figs.  VIII  and  IX. 

From  the  above  data  it  is  shown  conclusively  that  the 
presence  of  acid  or  alkali  does  have  a  marked  effect  upon  the 
osmose  of  salt  solutions. 

It  is  also  clearly  shown  that  the  presence  of  acid  or  alkali 
may  alter  not  only  the  electrical  sign  of  the  capillary  wall 
system  but  also  may  alter,  or  even  reverse,  the  electrical  sign 
of  the  membrane  system. 

A  study  of  the  results  obtained  brings  out  the  fact  that 
the  direction  of  osmose,  as  also  its  magnitude,  is  closely  related 
to  the  electrical  orientation  of  the  cell  system.  Although 
different  salt  solutions  with  cations  of  the  same  valence  do  not 
behave  exactly  alike  under  all  conditions,  they  all  do  show 
similar  effects  which  may  be  considered  to  be  characteristic 
for  the  solutions  of  that  class.  For  the  purpose  of  simplifying 
the  analysis  of  results,  we  may  select  the  potassium  salt  as 
being  representative  of  those  with  univalent  cations,  mag- 
nesium salt  as  being  representative  of  those  with  divalent 
cations,  and  thorium  salt  as  being  representative  of  salt  with 
cation  with  a  valence  of  three  and  above. 


36 

Osmosis  of  Salt  Solutions  with  Acid  or  Alkali  throughout 
Cell.  Potassium  Chloride. — The  osmose  of  neutral  KC1  solu- 
tion is  abnormally  small;  its  cell  system  is  represented  by 
case  B. 


37 

In  the  presence  of  0.001  M  acid  to  0.01  M  acid  the  elec- 
trical orientation  of  the  cell  system  is  represented  by  case  D, 
which  is  productive  of  an  abnormally  high  positive  osmose. 


Fig    IX. 


38 

When  the  system  contains  acid  of  0 . 1  M  concentration 
or  greater,  the  electrical  orientation  of  the  system  is  repre- 
sented by  case  C,  which  is  productive  of  abnormally  low  or 
even  negative  osmose. 

When  the  system  contains  alkali  throughout,  the  mem- 
brane is  in  every  case  electro-negative  and  the  electrical 
orientation  of  the  cell  system  is  represented  by  case  B,  which 
is  productive  of  abnormally  low,  or  negative,  osmose. 

Magnesium  Chloride. — The  factors  governing  the  osmose 
of  magnesium  chloride  are  identical  with  those  governing  the 
osmose  of  potassium  chloride.  The  same  explanations  given 
for  the  results  obtained  with  potassium  chloride  solutions 
apply  throughout  to  those  obtained  with  magnesium  chloride. 

Thorium  Chloride. — The  osmose  of  neutral  thorium 
chloride  solutions  is  abnormally  great  and  is  accounted  for 
by  the  fact  that  the  electrical  orientation  of  the  cell  system 
is  represented  by  case  D. 

An  exceedingly  small  amount  of  acid  present  in  the  cell 
system  lowers  the  potential  of  the  membrane  interface  system 
which,  as  a  result,  tends  to  lower  the  abnormally  great  positive 
osmotic,  tendency  of  thorium  chloride  solutions. 

A  still  greater  concentration  of  acid  throughout  the  sys- 
tem (0 . 1  M  and  above)  reverses  the  electrical  orientation  of 
the  membrane  system  giving  as  a  result  conditions  represented 
in  case  C.  The  resulting  osmose  now  becomes  abnormally 
low  or  even  negative. 

With  a  low  concentration  of  alkali  (0.0001  M)  throughout 
the  system  the  membrane  is  still  electro-positive  due  to  the 
pronounced  effects  of  the  quadrivalent  cation  of  the  salt 
solution.  The  conditions  are  represented  by  case  D,  and  an 
abnormally  great  positive  osmose  results. 

With  somewhat  higher  concentrations  of  alkali  throughout 
the  system,  the  sign  of  the  membrane  material  becomes  electro- 
negative; the  conditions  are  represented  by  case  B.  An 
abnormally  low  or  negative  osmose  results. 

It  was  mentioned  above  that  the  sign  of  the  gold  beaters 
skin  membrane  to  water  is  electro-negative.  The  iso-electric 


39 

point  of  this  membrane  is  reached  with  comparatively  low 
concentrations  of  acid,  approximately  0.0001  M.  In  the 
presence  of  different  salt  solutions  with  the  acid,  the  iso-electric 
point  comes  at  a  somewhat  different  concentration  with  each 
of  the  different  salts.  It  is  quite  likely  that  the  distinct 
breaks  noted  in  the  various  curves  (Fig.  VIII),  which  come  at 
about  0.0001  M  acid  concentration,  may  be  accounted  for 
by  the  fact  that  at  these  points  the  membrane  is  near,  or  is 
passing  through  the  iso-electric  point. 

It  is  hardly  necessary  for  the  writer  to  further  analyze 
the  results  obtained  with  the  various  solutions  under  the 
different  conditions  of  the  above  experiments.  The  same 
general  principles  apply  throughout.  It  may  be  stated  that 
many  experiments  in  addition  to  those  reported  in  this  paper 
have  been  carried  out  in  this  laboratory  during  the  past  eight 
years  in  which  this  investigation  has  been  in  progress,  and  in 
practically  every  case  the  results  obtained  may  be  explained 
when  the  factors  described  above,  are  determined  and  the 
principles  given  above  are  applied.  Experiments  similar 
to  the  above  have  been  carried  out  with  other  types  of  mem- 
branes. Considerable  work  has  been  done  with  membranes 
of  collodion ;  with  this  material  we  have  been  able  to  vary  the 
diameter  of  the  pore  spaces  as  well  as  the  thickness  of  the 
membrane.  Both  of  these  factors  are  important  in  the  con- 
sideration of  anomalous  osmose. 

UNIVERSITY  OP  MICHIGAN, 
ANN  ARBOR,  MICH. 


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40 

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30  Bartell  and  Hocker:  Loc.  cit. 

31  Bayliss:  Proc.  Roy.  Soc.,  848,  246  (1911). 

32  From  unpublished  data  obtained    n  this  laboratory. 


p  m.    . 

IB 


••m 


4587X3 


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